1. Field of the Invention
The present invention relates to a luminescent material transfer substrate for transferring a transfer layer including at least a luminescent layer by sublimation to a target object, a method for fabricating a display device using the transfer substrate, and a display device fabricated using the transfer substrate. More particularly, the invention relates to a method for fabricating a display device that includes organic electroluminescent elements and a display device that includes organic electroluminescent elements.
2. Description of the Related Art
Organic EL elements using electroluminescence (hereinafter referred to as “EL”) of organic materials have been receiving attention as light-emitting elements capable of achieving high-luminance light emission at low-voltage DC drive.
In full color organic EL display devices including organic EL elements, one of the important factors is to selectively disposing the individual luminescent organic materials as fine patterns on electrodes.
In order to fabricate a full color organic EL display device, since luminescent elements each emitting light of red (R), green (G), or blue (B) are arrayed on a substrate, organic layers each including at least a luminescent layer of any of these colors are formed. As one of the methods for fabricating such luminescent elements, a transfer method (i.e., thermal transfer method) using an energy source (heat source) has been proposed.
In the thermal transfer method, a thin film layer to be transferred is formed by vapor deposition, spin coating, printing, or the like on a transfer substrate, and after the thin film layer is attached to a substrate on which film formation is to be performed, energy such as laser light or heat is applied from the transfer substrate side. Subsequently, an organic layer on the transfer substrate is separated with the thin film layer being left partially or entirely, and thus the organic layer formed on the transfer substrate is transferred onto the substrate.
The advantage of the thermal transfer method is that patterning is not particularly required when a transfer layer is formed on a transfer substrate, and an organic layer is merely formed on the entire surface of the transfer substrate.
Only a portion irradiated with the heat source during transfer is transferred from the transfer substrate to the device-forming substrate. Thus, a high-definition pattern can be formed.
As the heat source used in the thermal transfer method, a laser is preferably used from the standpoint that high energy can be supplied locally. Furthermore, when scanning is performed with a laser beam having a reduced diameter, it is possible to form a line pattern very accurately, and higher definition is enabled.
In this method, however, it is necessary to sequentially scan a substrate with a laser beam while performing alignment with high accuracy, and thus it is difficult to improve productivity. In order to perform transfer while maintaining high productivity, it is desirable to design a structure in which laser irradiation can be performed on the entire surface of the transfer substrate or in which the desired transfer layer can be selectively transferred.
In consideration of the above, for example, Japanese Patent Nos. 2918037 and 3175733 each disclose a method in which a member having low thermal conductivity and a member having high thermal conductivity represented by copper (Cu) are patterned in advance onto a transfer substrate, and a desired organic layer is transferred using a laser, a heat bar, or the like as the heat source.